1. Field of the Invention
This invention relates generally to transverse flux electrical machines. The present invention more specifically relates to transverse flux alternators and motors assembly.
2. Description of the Related Art
Alternators and motors are used in a variety of machines and apparatuses to produce electricity from mechanical movements. They find applications for energy production and transportation, to name a few. Alternators and motors can use Transverse Flux Permanent Magnet (TFPM) technologies.
Transverse flux machines with permanent magnet excitation are known from the literature, such as the dissertation by Michael Bork, Entwicklung and Optimierung einer fertigungsgerechten Transversalfluβmaschine [Developing and Optimizing a Transverse Flux Machine to Meet Production Requirements], Dissertation 82, RWTH Aachen, Shaker Verlag Aachen, Germany, 1997, pages 8 ff. The circularly wound stator winding is surrounded by U-shaped soft iron cores (yokes), which are disposed in the direction of rotation at the spacing of twice the pole pitch. The open ends of these U-shaped cores are aimed at an air gap between the stator and rotor and form the poles of the stator. Facing them, permanent magnets and concentrators are disposed in such a way that the magnets and concentrators that face the poles of a stator core have the opposite polarity. To short-circuit the permanent magnets, which in the rotor rotation are intermittently located between the poles of the stator and have no ferromagnetic short circuit, short-circuit elements are disposed in the stator.
Put otherwise, transverse flux electrical machines include a circular stator and a circular rotor, which are separated by an air space called air gap, that allows a free rotation of the rotor with respect to the stator, and wherein the stator comprises soft iron cores, that direct the magnetic flux in a direction that is mainly perpendicular to the direction of rotation of the rotor. The stator of transverse flux electrical machines also comprises electrical conductors, defining a toroid coil, which is coiled in a direction that is parallel to the direction of rotation of the machine. In this type of machine, the rotor comprises a plurality of identical permanent magnet parts, which are disposed so as to create an alternated magnetic flux in the direction of the air gap. This magnetic flux goes through the air gap with a radial orientation and penetrates the soft iron cores of the stator, which directs this magnetic flux around the electrical conductors.
In the transverse flux electrical machine of the type comprising a rotor, which is made of a plurality of identical permanent magnet parts, and of magnetic flux concentrators, the permanent magnets are oriented in such a manner that their magnetization direction is parallel to the direction of rotation of the rotor. Magnetic flux concentrators are inserted between the permanent magnets and redirect the magnetic flux produced by the permanent magnets, radially towards the air gap.
The transverse flux electrical machine includes a stator, which comprises horseshoe shaped soft iron cores, which are oriented in such a manner that the magnetic flux that circulates inside these cores, is directed in a direction that is mainly perpendicular to the axis of rotation of the rotor.
The perpendicular orientation of the magnetic flux in the cores of the stator, with respect to the rotation direction, gives to transverse flux electrical machines a high ratio of mechanical torque per weight unit of the electrical machine.
It is desirable that the magnets and the concentrators of the rotor of a transverse flux electrical machine be precisely mounted on the rotor to ensure a tight airgap with the stator portion when rotatably assembled with the stator portion.
It is also desirable that the rotor portion be rotatably mounted to an axial shaft with bearings and seals preventing any undesirable objects or dirt to get into the rotor portion.
One other desirable aspect consists in providing as strong and secure assembly of the concentrators and the magnets to the body of the rotor portion to prevent any undesirable removal of a concentrator and/or a magnet when the transverse flux electrical machine is in operation.
At least one aspect of the present invention provides an external rotor assembly adapted to rotate around the stator assembly to increase the effective airgap diameter while having a reduced overall stator and rotor assembly or, for example, to have a rotative external component.
It is therefore desirable to produce an electrical machine that is easy to assemble. It is also desirable to provide an electrical machine that is economical to produce. Other deficiencies will become apparent to one skilled in the art to which the invention pertains in view of the following summary and detailed description with its appended figures.